Maintenance of Distal Intestinal Structure in the Face of Prolonged Fasting: A Comparative Examination of Species From Five Vertebrate Classes

Abstract

It was recently shown that fasting alters the composition of microbial communities residing in the distal intestinal tract of animals representing five classes of vertebrates [i.e., fishes (tilapia), amphibians (toads), reptiles (leopard geckos), birds (quail), and mammals (mice)]. In the current study, we tested the hypothesis that the extent of tissue reorganization in the fasted distal intestine was correlated with the observed changes in enteric microbial diversity. Segments of intestine adjacent to those used for the microbiota study were examined histologically to quantify cross-sectional and mucosal surface areas as well as thicknesses of mucosa, submucosa, and tunica muscularis. We found no fasting-induced differences in the morphology of distal intestines of the mice (3d), quail (7d), or geckos (28d). The toads, which exhibited a general increase in phylogenetic diversity of their enteric microbiota with fasting, also exhibited reduced mucosal circumference at 14 and 21 days of fasting. Tilapia showed increased phylogenetic diversity of their enteric microbiota, and showed a thickened tunica muscularis at 21 days fasting; but this morphological change was not related to microbial diversity or absorptive surface area, and thus, is unlikely to functionally match the changes in their microbiome. Given that fasting caused significant increases and reductions in the enteric microbial diversity of mice and quail, respectively, but no detectable changes in distal intestine morphology, we conclude that reorganization is not the primary factor shaping changes in microbial diversity within the fasted colon, and the observed modest structural changes are more related to the fasted state.

Surviving on limited resources: effects of caloric restriction on growth, gene expression and gut microbiota in a species with male pregnancy (Hippocampus erectus)

“…Major differences were seen in the higher abundance of Proteobacteria (11.7%) and Bacteroidetes (7.8%) in CR compared to AL fed groups (1.95% and 0.97% respectively). These results are consistent with other studies showing a higher relative abundance of Bacteroidetes and Proteobacteria in fasting vertebrates (including fish) 108,110 . Bacteroidetes are known for their involvement in breaking down complex carbohydrates and producing short-chain fatty acids 111 and some members are also known to possess the capability to utilize mucosal glycans secreted by the host, thereby providing the host with extra energy 112 .…”

Gut microbiota modulation as a possible mediating mechanism for fasting-induced alleviation of metabolic complications: a systematic review

“…McCue MD, et al showed that prolonged fasting altered the composition of microbial communities residing in the distal intestinal tract of animals representing five classes of vertebrates. The major diversity was observed in Bacteriodetes, Firmicutes, Proteobacteria, Fusobacteria and Verrucomicrobia phyla, but no detectable change was shown in distal intestine morphology [ 20 ].…”

Dietary and Sexual Correlates of Gut Microbiota in the Japa-Nese Gecko, Gekko japonicus (Schlegel, 1836)

“…For instance, diet shapes gut microbiota in S. crocodilurus [17] but not in Varanus salvator [31]. Compared with other reptile taxa, studies on gut microbiota in geckos have been limited, focusing only on the effects of fasting on gut microbiota in Eublepharis macularius [32,33] and the structure of gut microbiota in Hemidactylus frenatus [34]. Here, we used high-throughput sequencing to study dietary and sexual correlates of the gut microbiota in the Japanese gecko, Gekko japonicus.…”